1. Field of the Invention
The present invention relates to a spindle motor provided with a chucking device for removably holding a disk and a disk drive apparatus provided with the spindle motor.
2. Description of the Related Art
In recent years, the rotating speed of a disk and a spindle motor for rotating the disk grows faster in keeping with the increase in the speed at which information is recorded on and reproduced from a disk such as a CD or a DVD. As a chucking device coping with the high-speed rotation of the disk, there is available a structure that includes a cone having an annular slant surface making contact with the entire perimeter of the inner circumferential surface of the central opening of the disk. The cone is movable along the axial direction of a rotating shaft. The cone is biased axially upward by a resilient member such as a coil spring or the like.
A turntable for supporting the disk is arranged around the cone. A rotor holder is arranged below the turntable.
In the spindle motor of the type stated above, the height of the spindle motor is limited in light of the specifications of the disk drive apparatus. Thus, when fixing the turntable to the shaft, it may be impossible to sufficiently secure the axial length along which the turntable and the shaft make contact with each other. This may lead to a shortage in the fastening strength. Accordingly, there is a need to bond and fix the turntable to at least the upper surface of the rotor holder.
In the meantime, the spindle motor is provided with an annular space for accommodating balancing steel balls. The space is defined by closing an upwardly depressed annular recess with an annular plate at the lower side of the recess. The annular plate is readily fixed in place by interposing the same between the body of the turntable and the rotor holder. Due to this structure, the turntable and the rotor holder are fixed together by an adhesive agent at the radial inner side of the annular recess.
When adhesively fixing the turntable and the rotor holder, a clearance of suitable size needs to be left between the turntable and the rotor holder. The bonding strength is changed depending on the size of the clearance. However, the size of the clearance varies with the thickness of the annular plate or the forming accuracy of the body of the turntable. In case where an attempt is made to reduce variations in the clearance size by increasing the form accuracy of parts, it becomes difficult to reduce the manufacturing cost.